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Seasonal variability of solar UV radiation in ocean waters is estimated on a global scale by combining satellite measurements of scene reflectivity (TOMS), column ozone (TOMS) and chlorophyll concentration (SeaWiFS) with radiative transfer calculations for an ocean-atmosphere system. The new features are an extension of underwater radiative transfer (scattering and absorption) into the UV, inclusion of polarization in the above water diffuse radiances, the proper treatment of Fresnel reflection, and first order atmospheric backscatter of water-leaving radiance to the oceans. Maps of downwelling diffuse irradiances (E d ) at ocean surface and at different depths in the ocean, diffuse attenuation coefficient (K d ), and ten percent penetration depth (Z 10 ) of solar irradiation are computed for open ocean waters. Results on spectral irradiances at 310 nm in UV-B and at 380 nm in UV-A part of the spectrum are presented with particular emphasis on the role of aerosols, clouds, and ozone in the atmosphere and chlorophyll concentrations in the ocean.

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Public reporting burden for this collection of information is estimated to average one hour per response, including the time tor reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of Information, Including suggestions for reducing the burden to Washington Headquarters Services. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)Office of The goal of this project was to develop a solar simulating UV-visible incubator to grow HAB dinoflagellates, to begin MAA analysis of samples collected on global cruises, and to carry out initial experiments on HAB dinoflagellate species in pure culture. Our scientific objectives are to quantify MAA production and spectral induction mechanisms in HAB species, to characterize spectral absorption of MAAs, and to define the ecological benefit of MAAs (i.e. photoprotection). Data collected on cruises to the global oceans will be used to parameterize phytoplankton absorption in the UV region, and this parameterization could be incorporated into existing models of seawater optical properties in the UV spectral region. Data collected in this project were used for graduate fellowship applications by Elizabeth Frame. She has been awarded an EPA STAR fellowship to continue the work initiated by this project. SUBJECT TERMS AbstractThe development of an enhanced predictive and early warning capability for the occurrence and impact of harmful algal blooms (HABs) would be of great benefit to coastal communities. A critical issue for early detection and monitoring of HABs is the need to detect harmful algal species within a mixed-species phytoplankton assemblage. Possession of UV-absorbing compounds called mycosporine-like amino acids (MAAs) may be one factor that allows HAB species to out-compete their phytoplankton neighbors. Possession of MAAs, which we believe can be inferred from strong UVabsorption signals in phytoplankton absorption coefficients, can be used as a flag for potential HAB outbreak. The goal of this project was to develop a solar simulating UVvisible incubator to grow HAB dinoflagellates, to begin MAA analysis of samples collected on global cruises, and to carry out initial experiments on HAB dinoflagellate species in pure culture. Our scientific objectives are to quantify MAA production and spectral induction mechanisms in HAB species, to characterize spectral absorption of MAAs, and to define the ecological benefit of MAAs (i.e. photoprotection). Data collected on cruises to the global oceans will be used to parameterize phytoplankton absorption in the UV region, and this parameterization could be incorporated into existing models of seawater optical properties in the UV spectral region. Data collected in this project were used for graduate fellowship applications by Elizabeth Frame. She has been awarded an EPA STAR fellowship to continue the work initiated by this project.

Overview of ONR sponsored research to Dr. B. Greg Mitchell, and long-range goals A thorough understanding of marine optics is a mission of significant Naval relevance. The ability to use optical measurements (in situ and remote)_to estimate light propagation and phytoplankton growth rates is a significant objective. This objective requires a detailed understanding of the nature and variability of source and loss terms, and an ability to model the relevant rates. Figure 1 summarizes dominant state variables and transformations occurring in marine optics, and the contributions by the principal investigator in understanding these processes. Several significant problems previously have not been resolved with respect to measuring or modeling the processes in Figure 1. The long-range objectives of the principal investigator is to continue studies of the various components and rate processes shown in Figure I in an effort to improve our understanding of marine optical properties and photo-physiology and ecology of phytoplankton. Figure 1. A conceptual model of optically important processes in the ocean. The long-range objectives of our research include a detailed understanding of the processes and state variables specified in this figure. The state variables in the boxes (S1-S6) correspond to dominant sources of optical variability in the oceans. The principal investigator has dedicated his research effort to understanding the diverse aspects of this system. Methods for estimating the magnitude and characteristics of Si, S2 and 53 have included analysis of particle absorption using microphotometry (Iturriaga et al, 1988); macrophotometry (Mitchell and Kiefer, 1984;Mitchell et al. 1984;Mitchell and Kiefer, 1988a;1988b; Mitchell, 1990); in situ optical profiling resulting in discovery of regional bio-optical relationships (Mitchell and HolmHansen, 1991a; Mitchell, 1992); a novel method to estimate S1 from moored radiometers (Stramski et al. 1992); and aircraft (Tanis et al., 1990) or satellite observations of biomass . Optical based models of phyoplankton photosynthesis for laboratory cultures (Kiefer and Mitchell, 1983; Sosik and Mitchell, 1991) for Antarctic phytoplankton (Mitchell and Hom-Hansen, 1991b) and for Arctic phytopplankton (Cota et al., 1992) have been developed to model process K1. Siegel et al. (1989) used an in situ optical approach to estimate K1 and K2+K5 for populations in the North Pacific Gyre. Carder et al. (1991) have used optical methods to partition S1 from S2 and S3 for remote sensing. Sedimentation rates of Antarctic and Arctic phytoplankton (K2) have been studied by Mitchell and Holm-Hansen (1991b) and Wassman et al., (1990). OBJECTIVS FOR GRANT N00014-J-90-1052The objectives of the work sponsored under ONR grant N00014-90-J-1052 was to apply the absorption methods developed during FY89 under grant N00014-89-J-1071. In FY89, the methodology of the Quantitative Filter Technique (OFT) Was verified and published. In FY90, the objectives were to utilize the methods in the study of specific ...